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Level 1

14 points

"An Error Occurred while preparing the installation. Try running this application again. Any OS.

I tried to do a clean installation with the High Sierra. AFTER the installation is completed, the following message appears: "An error occurred while preparing the installation.

I'VE ALREADY TRIED:

1) Change the date by Terminal. / Result: the date is already correct and even then when I try it appears "command not found"

2) I tried booting into Internet Recovery (command - option / alt - R on a restart). / Result: It took me to the native system of my mac (OS X v10.8 Mountain Lion) and when I went to install appeared the same error message after the complete installation.

3) I tried to download the High Sierra installer several times ... Same error message.

NOTE: The message appears AFTER the installation and not BEFORE as seen on the internet.

'm in Brazil and I downloaded the installer from the USA Apple Store, maybe it influenced the time zone?

Does anyone know what it could be?

Currently my computer is a Mac Mini Late 2012 - Mavericks.

Thank you.

Mac mini, Late 2012

Posted on Feb 18, 2018 4:00 PM

Best reply

harrouet

Level 1

14 points

Posted on Mar 27, 2018 3:08 AM

Hello,

I ran into the same issue while trying to factory-reset a Mac Mini 2012 with MacOS High Sierra from a USB key.

The Mac Mini had a custom Fusion Drive with High Sierra on it, and was previously formatted with APFS. The Fusion volume had been erased and reformatted with Journaled HFS+.

(@Apple technical staff: I hope this info helps you to improve the great products you are working on)

Just as in your case, the installation process went smoothly, up to the point where the installation disk contents where copied to the target volume, and Kaboom! : I got the screen as shown in Unable to install High Sierra - "an error occurred while preparing the installation"

As you may know, APFS on Fusion drives is currently at Beta stage, so glitches are to be expected.

As stated before, however, the Fusion drive had previously been erased with Disk Utility and reformatted as "Journaled MacOS Extended".

Here is how I solved the issue:

The issue came from the inability for the installer to unmount the Fusion drive before rebooting. I figured this out in Disk Utility as it could not unmount the drive to "repair" it.
So I used the instructions in the second part of this Apple documentation: APFS Fusion
- Open a Terminal window (in the Installer launch screen, it is under the "Utilities" menu item.
- Look for the Unix names of your drives:
  - #> diskutil list internal
  - take note of which drive is the SSD, which is the HDD. In my case, it was as in the example from Apple: SSD was disk0, HDD was disk1.
- Force-unmount your target logical volume:
  #> diskutil unmount force disk2s1
- Separately re-format each Drive of the previously-unmounted Fusion volume:
  - #> diskutil eraseDisk JHFS+ SSD disk0
  - #> diskutil eraseDisk JHFS+ HDD disk1
- Recreate a Fusion Drive:
  #> diskutil cs create "Macintosh HD" disk0 disk1
- Recreate a logical volume on it:
  diskutil cs createVolume "Macintosh HD" JHFS+ "Macintosh HD" 100%
- Quit the Terminal application. You'll be taken back to the installer.
Retry to install High Sierra. In my case the issue was completely solved.

Hope this helps, good luck!

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